Tibial component with enhanced radial cement fixation

ABSTRACT

A cemented tibial prosthesis having a bone-contacting surface with a porous outer rim. With the bone-contacting surface seated against a resected proximal tibia, bone cement or another suitable adhesive will travel into the pores of the porous outer rim to enhance the connection between the tibial prosthesis and the tibia.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication Ser. No. 61/236,988, entitled “TIBIAL COMPONENT WITHENHANCED RADIAL CEMENT FIXATION,” filed Aug. 26, 2009, the disclosure ofwhich is hereby expressly incorporated by reference herein in itsentirety.

BACKGROUND

1. Field of the Invention

The present invention relates to the field of orthopedics. Moreparticularly, the present invention relates to a cemented tibialprosthesis, and to a method for using the same.

2. Description of the Related Art

Orthopedic prostheses are commonly used to repair and replace damagedbone and tissue in the human body. For example, to repair damaged boneof the knee joint and to recreate the natural, anatomical articulationof the knee joint, a tibial prosthesis may be implanted in the proximaltibia and/or a femoral prosthesis may be implanted in the distal femur.

The tibial prosthesis may include a first, articulating component havinga concave articulating surface configured for articulation against anatural femur or a femoral prosthesis. The tibial prosthesis may alsoinclude a second, tray component having a bone-contacting surfaceconfigured for securing the tibial prosthesis to the bone stock of aresected proximal tibia. The articulating component may be made from apolymer to facilitate articulation with the adjacent femoral prosthesis,while the tray component may be made from a metal to provide additionalstrength and rigidity to the tibial prosthesis.

SUMMARY

The present invention provides a cemented tibial prosthesis having abone-contacting surface with a porous outer rim. With thebone-contacting surface seated against a resected proximal tibia, bonecement or another suitable adhesive will travel into the pores of theporous outer rim to enhance the connection between the tibial prosthesisand the tibia.

According to an embodiment of the present invention, a tibial prosthesisis provided that is configured for securement to a patient's tibia andfor articulation with an adjacent femoral component. The tibialprosthesis includes an articulating component and a tray component. Thearticulating component has a concave articulating surface to facilitatearticulation with the femoral component. The tray component is coupledto the articulating component, the tray component having abone-contacting surface that is configured for securement to thepatient's tibia, the bone-contacting surface having an outer edge, thebone-contacting surface including an interior region and an outer porousregion, the outer porous region of the bone-contacting surface having ahigher porosity than the interior region of the bone-contacting surface,the outer porous region of the bone-contacting surface extending alongthe outer edge to at least partially surround the interior region of thebone-contacting surface.

According to another embodiment of the present invention, a tibialprosthesis is provided that is configured for securement to a patient'stibia and for articulation with an adjacent femoral component. Thetibial prosthesis includes an articulating component and a traycomponent. The articulating component has a concave articulating surfaceto facilitate articulation with the femoral component. The traycomponent is coupled to the articulating component, the tray componenthaving a bone-contacting surface that is configured for securement tothe patient's tibia and at least one anchor that extends distally fromthe bone-contacting surface, the bone-contacting surface including aninterior region and an outer porous region, the outer porous region ofthe bone-contacting surface having a higher porosity than the interiorregion of the bone-contacting surface and being spaced further from theat least one anchor than the interior region of the bone-contactingsurface.

According to yet another embodiment of the present invention, a tibialprosthesis is provided for securement to a resected surface of apatient's tibia and for articulation with an adjacent femoral component,the resected surface of the patient's tibia having an interior area anda peripheral area surrounding the interior area. The tibial prosthesisincludes an articulating component and a tray component having abone-contacting surface with an interior region and an outer porousregion, the outer porous region of the bone-contacting surface having ahigher porosity than the interior region of the bone-contacting surface,the tibial prosthesis configured for securement to the patient's tibiawith the bone-contacting surface of the tray component facing theresected surface of the patient's tibia, the interior region of thebone-contacting surface facing the interior area of the resected surfaceand the outer porous region of the bone-contacting surface facing theperipheral area of the resected surface and surrounding a majority ofthe interior area of the resected surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a proximal perspective view of an exemplary tibial prosthesisof the present invention implanted in a resected proximal tibia, thetibial prosthesis including a first, articulating component mounted atopa second, tray component;

FIG. 2 is a proximal perspective view similar to FIG. 1 of the traycomponent implanted in the resected proximal tibia, the tibialprosthesis shown without the articulating component mounted atop thetray component; and

FIG. 3 is a distal perspective view of the tray component of FIG. 1.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate exemplary embodiments of the invention and suchexemplifications are not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION

Referring to FIG. 1, an exemplary tibial prosthesis 10 is shownimplanted in a resected proximal tibia T. Tibial prosthesis 10 includesa first, articulating component 20 mounted atop a second, tray component30.

As shown in FIG. 1, articulating component 20 of tibial prosthesis 10includes at least one concave articulating surface 22 configured forarticulation against a natural femur (not shown) or a femoral prosthesis(not shown). To facilitate articulation with an adjacent femoralcomponent, articulating component 20 of tibial prosthesis 10 may beconstructed of a smooth, abrasion-resistant material. Also, to providecushioning to the knee joint, articulating component 20 of tibialprosthesis 10 may be constructed of a resilient, deformable material.For example, articulating component 20 may be constructed of abiocompatible polymer, including, but not limited to, a hydrogel, polyether ether ketone, fiber reinforced poly ether ether ketone, ultrahighmolecular weight polyethylene, crosslinked ultrahigh molecular weightpolyethylene, or polyether ketone ether ether ketone. It is also withinthe scope of the present invention that articulating component 20 may beconstructed of a more rigid material like a biocompatible ceramic.Suitable ceramics include oxide ceramics, such as alumina or zirconia,and non-oxide ceramics, such as silicon nitride or silicon carbide.

Referring next to FIGS. 2 and 3, tray component 30 of tibial prosthesis10 is substantially U-shaped with posterior recess 31 being sized andshaped to receive the patient's posterior cruciate ligament (PCL). Traycomponent 30 of tibial prosthesis 10 includes a substantially planar,proximal receiving surface 32 and a substantially planar, distalbone-contacting surface 34 located opposite receiving surface 32. Traycomponent 30 of tibial prosthesis 10 also includes peripheral wall 36that extends between receiving surface 32 and bone-contacting surface34. As shown in FIG. 3, bone-contacting surface 34 of tray component 30is substantially U-shaped, having outer edge 42 that borders peripheralwall 36.

To provide strength and rigidity to tibial prosthesis 10, tray component30 may be constructed of a rigid biocompatible ceramic or metal. Forexample, tray component 30 may be constructed of titanium, a titaniumalloy, a zirconium alloy, tantalum, cobalt chromium, or cobalt chromiummolybdenum.

As shown in FIG. 2, receiving surface 32 of tray component 30 isconfigured to receive and mate with articulating component 20 (FIG. 1).Peripheral wall 36 of tray component 30 extends proximally beyondreceiving surface 32 to define an outer rim or lip 38. Receiving surface32 and rim 38 of tray component 30 cooperate to define chamber 40.According to an exemplary embodiment of the present invention, whenarticulating component 20 is received within chamber 40 of traycomponent 30 as shown in FIG. 1, articulating component 20 rests againstreceiving surface 32 of tray component 30 and is supported externally byrim 38 of tray component 30.

Articulating component 20 may be attached to tray component 30 via aninterference fit, with a mechanical fastener, or with an adhesive, forexample. Also, some or all portions of rim 38 may include flange 39 thatprojects inwardly into chamber 40. In this embodiment, articulatingcomponent 20 may include a groove (not shown) that is sized to receiveflange 39 of rim 38 in a tongue and groove arrangement to preventarticulating component 20 from lifting off of tray component 30.

As shown in FIG. 3, bone-contacting surface 34 of tray component 30 isconfigured for securement to the bone stock of a resected proximal tibiaT (FIG. 2). An exemplary attachment method involves using an adhesive,such as bone cement, which may not only provide a secure connectionbetween tray component 30 and tibia T, but may also strengthen tibia T.The adhesive may be any known medical grade adhesive having sufficientstrength to secure tray component 30 to tibia T, including, but notlimited to, light curable acrylic adhesives, acrylic adhesives,cyanoacrylate adhesives, silicone adhesives, urethane adhesives, epoxyadhesives, and bone cement.

Tray component 30 includes stem 44 and keel 46 that extend distally fromthe center of bone-contacting surface 34, as shown in FIG. 3. Inoperation, with bone-contacting surface 34 of tray component 30 seatedagainst the resected proximal tibia T (FIG. 2), stem 44 and keel 46 oftray component 30 extend into the intramedullary canal of tibia T tostabilize tray component 30 and to prevent rotation of tray component 30relative to tibia T. The intramedullary canal of tibia T may be filledwith bone cement or another suitable adhesive to anchor stem 44 and keel46 in place.

Tray component 30 further includes pockets 48 that are recessed intobone-contacting surface 34, as shown in FIG. 3. In operation, withbone-contacting surface 34 of tray component 30 seated against theresected proximal tibia T (FIG. 2), pockets 48 of tray component 30provide gaps between tray component 30 and tibia T for receiving bonecement or another suitable adhesive.

As shown in FIG. 3, bone-contacting surface 34 of tray component 30includes porous outer rim 50 that substantially or entirely surroundstray component 30 along outer edge 42. In this embodiment,bone-contacting surface 34 of tray component 30 is cooperatively definedby porous outer rim 50 and a solid or non-porous interior region 52 thatis less porous than porous outer rim 50. Porous outer rim 50 may includea strip of porous material that is inlayed into and bonded to traycomponent 30, such that porous outer rim 50 is generally flush withnon-porous interior region 52 of bone-contacting surface 34. In theillustrated embodiment of FIG. 3, porous outer rim 50 is radially spacedfrom non-porous interior region 52 of bone-contacting surface 34, andfrom stem 44, keel 46, and pockets 48, that extend distally from orproximally into non-porous interior region 52 of bone-contacting surface34, all of which are more centrally located on tray component 30 thanporous outer rim 50. In operation, with bone-contacting surface 34 oftray component 30 seated against the resected proximal tibia T (FIG. 2),bone cement or another suitable adhesive will travel into the pores ofporous outer rim 50 to enhance the connection between tray component 30and tibia T, especially along outer edge 42 of bone-contacting surface34.

According to an exemplary embodiment of the present invention, porousouter rim 50 extends entirely to outer edge 42 of bone-contactingsurface 34. It is also within the scope of the present invention thatporous outer rim 50 may be spaced apart slightly from outer edge 42 ofbone-contacting surface 34 while still being considered to extend alongouter edge 42 of bone-contacting surface 34. For example, porous outerrim 50 may be spaced apart from outer edge 42 of bone-contacting surface34 by approximately 1 mm, 2 mm, or 3 mm.

The width of porous outer rim 50 may vary depending upon the size oftray component 30 and/or the needs of a particular patient. In certainembodiments, porous outer rim 50 may have a width as small asapproximately 1 mm, 3 mm, or 5 mm and as large as approximately 10 mm,13 mm, 15 mm, or more. It is also within the scope of the presentinvention that the width of porous outer rim 50 may vary across theperimeter of tray component 30. For example, the medial/lateral width ofporous outer rim 50 may exceed the anterior/posterior width of porousouter rim 50.

Porous outer rim 50 of bone-contacting surface 34 may account forapproximately 3%, 5%, 10%, 15%, 20%, or more of the total undersidesurface area of tray component 30, with non-porous interior region 52 ofbone-contacting surface 34, stem 44, keel 46, and pockets 48, accountingfor the remaining 80%, 85%, 90%, 95%, or 97% of the underside surfacearea of tray component 30.

The present inventors have recognized that traction forces and pulsingforces on tibial prosthesis 10 reach a maximum level along peripheralwall 36 and rim 38 of tray component 30. Due to these high forces alongperipheral wall 36 and rim 38 of tray component 30, the presentinventors have observed from X-rays that implanted tray components 30begin detaching from the bone stock of tibia T and the adhesive layeralong the adjacent outer edge 42 of bone-contacting surface 34. Porousouter rim 50 of the present invention may strengthen the connectionbetween tray component 30 and tibia T, especially along outer edge 42 ofbone-contacting surface 34, to prevent such separation from tibia T whentray component 30 is exposed to anatomical forces. Also, the materialcost of tray component 30 having porous outer rim 50 may be less thanthe material cost of tray component 30 that is completely coated with orconstructed entirely of a porous material. Moreover, becausebone-contacting surface 34 of tray component 30 may include non-porousinterior region 52 and cement pockets 48, a surgeon should not mistaketray component 30 for a non-cemented prosthesis that may be attached totibia T primarily via bone ingrowth.

Porous outer rim 50 of tray component 30 may be constructed of a porousmaterial having adequately sized pores for receiving bone cement oranother suitable adhesive. For example, porous outer rim 50 may includea beaded material, a woven material, or a wire mesh material. Anexemplary metallic wire mesh material includes Sulmesh generallyavailable from Zimmer GmbH of Winterthur, Switzerland. Such materialsmay be less expensive than highly porous biomaterials designed toencourage bone ingrowth. However, it is within the scope of the presentinvention that porous outer rim 50 may be constructed of a highly porousbiomaterial. An exemplary highly porous biomaterial is produced usingTrabecular Metal™ technology generally available from Zimmer, Inc., ofWarsaw, Ind. Trabecular Metal™ is a trademark of Zimmer, Inc. Such amaterial may be formed from a reticulated vitreous carbon foam substratewhich is infiltrated and coated with a biocompatible metal, such astantalum, by a chemical vapor deposition (“CVD”) process in the mannerdisclosed in detail in U.S. Pat. No. 5,282,861, the disclosure of whichis expressly incorporated herein by reference.

While this invention has been described as having preferred designs, thepresent invention can be further modified within the spirit and scope ofthis disclosure. This application is therefore intended to cover anyvariations, uses, or adaptations of the invention using its generalprinciples. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

1. A tibial prosthesis configured for securement to a patient's tibiaand for articulation with an adjacent femoral component, the tibialprosthesis comprising: an articulating component having a concavearticulating surface to facilitate articulation with the femoralcomponent; and a tray component coupled to the articulating component,the tray component having a bone-contacting surface that is configuredfor securement to the patient's tibia, the bone-contacting surfacehaving an outer edge, the bone-contacting surface including an interiorregion and an outer porous region, the outer porous region of thebone-contacting surface having a higher porosity than the interiorregion of the bone-contacting surface, the outer porous region of thebone-contacting surface extending along the outer edge to at leastpartially surround the interior region of the bone-contacting surface.2. The tibial prosthesis of claim 1, wherein the outer porous region ofthe bone-contacting surface extends along the entire outer edge suchthat the outer porous region encloses the interior region of thebone-contacting surface.
 3. The tibial prosthesis of claim 1, whereinthe outer porous region of the bone-contacting surface is locatedradially outward from a center of the tray component.
 4. The tibialprosthesis of claim 1, wherein the tray component further includes atleast one cement pocket recessed into the bone-contacting surface. 5.The tibial prosthesis of claim 4, wherein the at least one cement pocketis recessed into the interior region of the bone-contacting surface, theat least one cement pocket being located radially inward of the outerporous region of the bone-contacting surface.
 6. The tibial prosthesisof claim 4, wherein the at least one cement pocket is directly borderedby the outer porous region of the bone-contacting surface, the outerporous region defining a rim of the at least one cement pocket.
 7. Thetibial prosthesis of claim 1, wherein the tray component furtherincludes at least one anchor extending distally from the bone-contactingsurface.
 8. The tibial prosthesis of claim 7, wherein the at least oneanchor extends distally from the interior region of the bone-contactingsurface, the at least one anchor being located radially inward of theouter porous region of the bone-contacting surface.
 9. The tibialprosthesis of claim 1, wherein the interior region and the outer porousregion of the bone-contacting surface are substantially flush to definea substantially planar bone-contacting surface.
 10. The tibialprosthesis of claim 1, wherein the outer porous region of thebone-contacting surface has a width between approximately 1 mm and 15mm.
 11. A tibial prosthesis configured for securement to a patient'stibia and for articulation with an adjacent femoral component, thetibial prosthesis comprising: an articulating component having a concavearticulating surface to facilitate articulation with the femoralcomponent; and a tray component coupled to the articulating component,the tray component having a bone-contacting surface that is configuredfor securement to the patient's tibia and at least one anchor thatextends distally from the bone-contacting surface, the bone-contactingsurface including an interior region and an outer porous region, theouter porous region of the bone-contacting surface having a higherporosity than the interior region of the bone-contacting surface andbeing spaced further from the at least one anchor than the interiorregion of the bone-contacting surface.
 12. The tibial prosthesis ofclaim 11, wherein the outer porous region of the bone-contacting surfacecompletely surrounds the at least one anchor and the interior region ofthe bone-contacting surface.
 13. The tibial prosthesis of claim 11,wherein the tray component further includes at least one cement pocketrecessed into the bone-contacting surface, the outer porous region ofthe bone-contacting surface at least partially surrounding the at leastone cement pocket.
 14. The tibial prosthesis of claim 13, wherein the atleast one cement pocket is directly bordered by the outer porous regionof the bone-contacting surface.
 15. The tibial prosthesis of claim 11,wherein the interior region and the outer porous region of thebone-contacting surface are substantially flush to define asubstantially planar bone-contacting surface.
 16. The tibial prosthesisof claim 11, wherein the outer porous region of the bone-contactingsurface has a width between approximately 1 mm and 15 mm.
 17. The tibialprosthesis of claim 11, wherein the bone-contacting surface has an outeredge, the outer porous region of the bone-contacting surface extendingalong the outer edge.
 18. A tibial prosthesis configured for securementto a resected surface of a patient's tibia and for articulation with anadjacent femoral component, the resected surface of the patient's tibiahaving an interior area and a peripheral area surrounding the interiorarea, the tibial prosthesis comprising: an articulating component; and atray component having a bone-contacting surface with an interior regionand an outer porous region, the outer porous region of thebone-contacting surface having a higher porosity than the interiorregion of the bone-contacting surface, the tibial prosthesis configuredfor securement to the patient's tibia with the bone-contacting surfaceof the tray component facing the resected surface of the patient'stibia, the interior region of the bone-contacting surface facing theinterior area of the resected surface and the outer porous region of thebone-contacting surface facing the peripheral area of the resectedsurface and surrounding a majority of the interior area of the resectedsurface.
 19. The tibial prosthesis of claim 18, wherein the traycomponent further includes at least one cement pocket recessed into thebone-contacting surface, the outer porous region of the bone-contactingsurface and the at least one cement pocket configured to receive bonecement.
 20. The tibial prosthesis of claim 18, wherein the traycomponent further includes at least one anchor extending distally fromthe bone-contacting surface, the at least one anchor sized for insertioninto the interior area of the patient's tibia.